176 THE ROMAN COMAGMATIC REGION. 
Pleistocene (Quaternary), and in some cases have continued into the present time. 
There does not seem to be any good evidence in favor of a regular shifting of the 
volcanic foci along the line in any direction, that is, that the volcanic action began 
successively later either northwardly or southwardly. On the contrary it is quite 
clear that some of them have been active simultaneously, or at least that the periods 
of activity have overlapped. 
But there seems to be no doubt of the fact that the extinction of activity has 
shifted southerly, and that the more northern volcanoes were extinct before the 
more southern ones. That this extinction was successive in a general way, though 
possibly with some irregularities, seems also to be true. Thus the Vulsinian vol- 
canoes, which began before those of the Campanian District according to Moderni, 
the Ciminian and the Sabatinian have all suffered much from erosion, so much 
so as to have lost much of their original forms. The Latian Volcano seems to have 
been active in the year 639 B. c. (114 A. u. c.), if we can believe the story of Livy* 
as to a shower of ashes from Mount Albanus. The age of the Hernican volcanoes 
is uncertain, but they were probably extinct before the Latian, as we have no records 
of an eruption in historic times. There is some evidence going to show that the 
Auruncan Volcano was active during Roman times, and the date 269 B. c. has 
been assigned to one eruption. But the evidence is not conclusive, and the general 
silence on the part of the Latin authors makes one somewhat skeptical as to so 
recent a date.| The modern activity of Vesuvius is too well known to need more 
than mention, while the last-recorded eruption of Ischia was in 1302, and that of 
the Phlegrean Fields in 1538 at Monte Nuovo, although the Solfatara Volcano is 
still emitting hot vapors. 
ORDER OF SUCCESSION OF TYPES. 
A much more detailed study of the various districts than the writer was able 
to give and an extensive collation of the literature are needed before this matter 
can be satisfactorily treated. From such observations as were made, however, 
and from a general survey of the literature, it would appear that no definite and 
constant order of succession obtains in the region. Salic types sometimes precede 
and sometimes follow the more femic ones, those with leucite sometimes underlie 
and sometimes overlie those without leucite. Instances of both kinds could be 
cited from the more complex districts, the Vulsinian, Ciminian, Sabatinian, and 
Auruncan. An order which seems to hold good in general, though with exceptions, 
in one district is contradicted by the facts of another. Indeed, so varied are the 
relations in this respect that the only general law which can be laid down for the 
region, at least for the present, is that there is no definite order of succession. 
* Cf. V. Sabatini, Mem. Descr. Carta Geol. Ital., X, 1900, p. 132. 
t P. M oderni, Boll. Com. Geol. Ital., 1887, p. 77. 
